A conventional gas cooking appliance, such as a gas cook top, includes a plurality of gas burners arranged in an array on the cook top. The burners are supplied from a manifold connected to a source of fuel gas, with individual user operated valve control dials for regulating the flow of gaseous fuel to the individual burners. Food to be cooked is placed in receptacles, e.g., pots and pans, which are positioned over the burners on the gas cook top.
Typical gas burners have an annular or generally ring-shaped configuration, with flame-generating ports disposed peripherally around the burner to provide a ring of discrete flames emanating from the burner ports when the user operates a control valve to provide a flow of gas to the burner. (The burner flame may be ignited by a continually burning pilot flame positioned in or near the burner or, more commonly, by an electrical flame ignition.) One limitation of such conventional burners is that they cannot provide a wide range of heating capability, ranging from very high firing rates (low-time-to-boil) to low (simmer) capability. If the burner ports are made large, to accommodate a high gas flow therethrough for providing high output, the flame provided by such ports will extinguish if the gas flow is reduced too much. Similarly, if the burner ports are made small, to support a low firing rate, for simmering, the flow through the burner ports will be restricted, causing the flames to lift off at higher gas flow levels, thereby limiting high firing rate capability of the burner.
A conventional dual gas burner attempts to achieve both good high firing rate and simmer performance by utilizing two burner rings in each burner. Concentric main and simmer burners are provided, with the main outer and larger burner having more and larger burner ports than the burner ports provided in the smaller and inner simmer burner. Gas flow to the main and simmer burners is controlled to provide high firing rates by providing gas flow at relatively high rates to the main burner, and low firing rates, for simmering, by providing gas flow at a lower rate to the simmer burner. In such configurations, the small inner burner has very good convective heat transfer to a container located over the burner in which food to be cooked is placed, thereby raising the effective simmer temperature. Simultaneously, the larger outer burner ring has poor convective heat transfer to the cooking container, thus increasing time to boil at high firing rates. Thus, this conventional burner configuration in itself is of limited effectiveness, providing more heat to a cooking container when it should be providing less (during simmering), and less heat when it should be provide more (at high firing rates).
Another method which has been used to achieve good simmer performance may be employed with a single conventional burner ring. To achieve low output from such a burner, without unintentional loss of flame, gas flow is maintained at a level to keep the flame burning, but the gas flow is cycled on and off at a low duty cycle to keep temperatures minimized. Shutting off the gas flow for variable short periods of time can reduce the average heat output below that output possible with the control of only the continuous flow rate, thereby providing good simmer performance. However, such burners require an additional control system and added hardware which increases the manufacturing costs and reduces the reliability of gas cook tops employing such burners. Also, the cyclic nature of the burner operation can be less safe than other methods.
What is desired, therefore, is a low-cost gas burner for a gas cook top or other gas cooking appliance which can achieve good performance (low-time to-boil, high efficiency, and low emissions) at high firing rates as well as good simmer performance at low firing rates.